1. Field of the Invention
Embodiments of the present invention mainly relate to fuel vapor processing apparatus, in which fuel vapor is adsorbed by an adsorption material contained in a container, the fuel vapor adsorbed by the adsorption material is desorbed (or purge) during driving of an engine, find a heater is provided for heating the adsorption material for promoting desorption of fuel vapor.
2. Description of the Related Art
A known fuel vapor processing apparatus configured as described above is disclosed in JP-A-2002-332922. The known fuel vapor processing apparatus has a container having an internal space divided into a main adsorption chamber and an auxiliary adsorption chamber. Each of the main and auxiliary adsorption chambers has an ad sorption material contained therein and also has a heater for heating the adsorption material. The main adsorption chamber communicates with a tank port and a purge port. The tank port is connected to a fuel tank that may produce fuel vapor. The purge port communicates with an intake pipe of an engine. The auxiliary adsorption chamber communicates with an atmospheric port for introduction of the atmospheric air. The tank port and the purge port communicating with the main adsorption chamber are positioned adjacent to each other. One side of the main adsorption chamber positioned further from the tank port and the purge port communicates with one side of the auxiliary chamber positioned further from the atmospheric port.
Fuel vapor produced within the fuel tank may enter the main adsorption chamber via the tank port and may be adsorbed by the adsorption material contained in the main adsorption chamber. Apart of the fuel vapor that has not been adsorbed by the adsorption material of the main adsorption chamber may flow from the main adsorption chamber into the auxiliary adsorption chamber and may be adsorbed by the adsorption material contained in the auxiliary adsorption chamber. As the engine is driven, the air may be drawn from, within the container into the engine via the purge port, so that air may flow into the container. In this way, the fuel vapor may be desorbed from the adsorption materials. As she fuel vapor is desorbed from the adsorption materials, the adsorption materials may be cooled to cause reduction in the adsorption ability. However, the heat of the heaters may inhibit such cooling of the adsorption materials.
After the engine has been stopped, desorption of fuel vapor by the flow of air may not occur. However, in this state, it may be necessary to inhibit fuel vapor that has been once adsorbed by the adsorption materials from being released to the atmosphere. To do this, it may be necessary to reduce in advance at least the fuel vapor adsorbed by a part of the adsorption material positioned near the atmospheric air introduction port. In order to enable this reduction, it may be necessary to design the heater to have a large heating capacity for promoting desorption. However, making the heating capacity larger is not preferable because the energy consumption may be increased.
Therefore, there has been a need in the art for a fuel vapor processing apparatus that can increase the fuel vapor desorption ability of a part of the adsorption material positioned nearer to the atmospheric air introduction, portion without need of increasing the heating capacity of the heater.